Detectable stainless steel needles for meat packing

ABSTRACT

Magnetic stainless steel needles are detectable in processed meat. The previous non magnetic versions, made of 304 stainless steel, aren&#39;t. Disposable hypodermic needles made from martensitic and ferritic stainless steel are easily detectable at the smallest size. Needles are conveniently made from 420 martensitic stainless steel or 430 ferritic stainless steel.

This invention relates to a new use of stainless steel. Stainless steelhypodermic needles are used in raising livestock to be processed in meatpacking plants. The needles break leaving metal in processed meat.Although metal detectors are employed in most meat packing plants,currently they don't detect stainless steel needles in meat.

BACKGROUND

Needles, which have broken off in livestock, are a problem in processedmeat. Although disposable, in the field they are used repeatedly untilthey snap or break off in livestock (pigs and cattle). The needle has astainless steel cannula fixed in a hub. The cannula breaks away from thehub or the cannula itself breaks, and remains unrecovered in the animal.Hubs are generally plastic (often polypropylene), aluminum, or chromiumcoated brass. Broken needles are more common in pork than beef becauseof the sheer volume of pigs processed each year. Needles will be presentin processed meat from all livestock subject to injection. The currentdisposable needles used in the raising of livestock are usually made of304 stainless steel, an austenitic alloy typically about 18 to 20%chromium and 8 to 12% nickel. It is not magnetic and needles made of itare not detectable by metal detectors currently used in meat plants, norare other disposable hypodermic needles made of non-magnetic metals andalloys. One hundred million disposable hypodermic needles are usedyearly. The current usage of disposable needles in the raising oflivestock causes them to break. These undetectable needles end up inprocessed meat and pass through packing plants, which are sold toconsumers, domestically and internationally. Many meat packing plants inNorth America use metal detectors in an attempt to detect and removedisposable hypodermic needles from processed meat. Despite this practicefew, if any, disposable needles are detected and removed. For allpractical purposes disposable hypodermic needles of austenitic 304stainless steel and other non-magnetic metals and alloys are notdetectable.

The problem is as at least as old as disposable hypodermic needles, andthe meat packing industry is well aware of it. The problem has not beenaddressed by the needle manufacturers, who are also aware of theproblem. The suggestion sometimes made that the stainless steeldisposable needles should not be used in livestock raising, or at anyrate not repeatedly used, is fanciful and not at all practical.

Although this suggestion is obviously ridiculous it is the solesuggestion to emerge from an in depth study at the Iowa StateUniversity, Ames (Hoff et. al., American Journal of Veterinary Research,60, No.3, 292-298, 1999) which concluded that stainless steel needlesand their hubs were sufficiently resilient to avoid breakage in singleuse. The contributory factor of breakage is that the animal moves wheninjected deforming the needle. The prime cause of breakage is that thedeformed needle is straightened by hand and reused. The needle whenstraightened is much more likely to break off in the animal, and thechance increases with repeated straightening. While the manufacturersplace product notices on needle packaging specifying “single use only”,this is not followed in practice. The Iowa study also recommended“single use only.”

There is increasing worry about disposable needles in the processed meatindustry especially since complaints and presumably incidence areincreasing. Export contracts are especially sensitive to the discoveryof needles in meat. Two surveys were carried out in 1999 in Canada bythe Canadian Cattlemen, a trade publication; one of veterinarians, oneof processors, purveyors and retailers. The veterinarians (25% of whomhad experienced broken needles) recommended use of proper animalrestraints (50%, but difficult in practice), restricted reuse of theneedle 5 to 20 times (41%), and discarding damaged needles (28%). Of theproducers 41% had from 1 to 12 complaints about needles in the averageyear, 30% had metal detectors, and 31% used metal detectors (14%supplemented by visual inspection), about 14% passed all productsthrough a metal detector, and another 14% passed some products through ametal detector. About 73% had high confidence in metal detection in trim(not whole muscle), 18% medium and 9% low. The surveys as summarized(Donkersgoed, Canadian Cattlemen, January 2000, p. 28) stated that theprocessors had little confidence in the ability of metal detectors todetect metal in large cuts of meal. As noted above, austenitic stainlesssteel is non-magnetic and one of the hardest metals to detect using ametal detector.

There are four groups involved, the needle manufacturers, veterinarians,producers, meat packers. Neither the packer nor the producer can rely onthe other to detect needles in meat. In practice the packer is liable,because it is difficult if not impossible to identify the producer.Although some meat packing plants use metal detectors these are rarelysuccessful in detecting needles.

There is therefore a need for detectable disposable needles. Currentcommon needles come in several sizes especially 20 gauge×½ inch, 18gauge×1 inch, 18 gauge×1½ inch, 16 gauge×1 inch, 16 gauge×1½ inch, 14gauge×1 inch, 14 gauge×1½inch, with larger needles used for largeranimals and smaller needles for smaller animals. The primary need is todetect the smallest needles when broken off (20 gauge×½ inch), andpreferably smaller broken portions of such needles.

PRIOR ART

Applicant is not aware of any prior art.

It is a principal object of the invention to provide hypodermic needlesdetectable in meat by metal detectors currently used in meat packingplants. It is a subsidiary object of the invention to provide hypodermicneedles detectable in meat as broken portions by metal detectorscurrently used in meat packing plants.

DESCRIPTION OF THE INVENTION

The invention in its broadest aspect is directed to a magnetic stainlesssteel hypodermic needle detectable in meat by metal detectors. Themagnetic stainless steel is preferably selected from the group offerritic and martensitic stainless steels. The stainless steel may beferritic, preferably 430 stainless steel, or it may be martensitic,preferably 420 stainless steel. The needle is preferably of length from½ to 1½ inches long and gauge from 14 to 20. The needle may be of length½ inch and gauge 20, of length 1 inch and gauge 18, of length 1½ inchand gauge 18, of length 1 inch and gauge 16, of length 1½ inch and gauge16, of length 1 inch and gauge 14, of length 1½ inch and gauge 14.

In another aspect the invention is directed to the novel use of magneticstainless steel in disposable hypodermic needles, detectable in meat bymetal detectors. The magnetic stainless steel is preferably selectedfrom the group consisting of ferritic and martensitic stainless steel.More preferably the stainless steel is martensitic stainless steel,conveniently 420 stainless steel. Also more preferably the stainlesssteel is ferritic stainless steel, conveniently 430 stainless steel.

In another aspect the invention is directed to the manufacture ofdisposable hypodermic needles detectable in meat by metal detectors frommagnetic stainless steel. The magnetic stainless steel is preferablyselected from the group consisting of ferritic and martensitic stainlesssteel. More preferably the stainless steel is martensitic stainlesssteel, conveniently 420 stainless steel. Also more preferably thestainless steel is ferritic stainless steel, conveniently 430 stainlesssteel. The preferred method of manufacture is cold drawing of tubularstock, which typically requires several iterations.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is illustrated but not restricted by reference to thepreferred embodiments. It is well known that austenitic stainless steelsare non-magnetic, and almost impossible to detect using metal detectors,which rely on distortion of an oscillating electromagnetic field. Thereason is that non-magnetic stainless steel is a relatively poorconductor of electric current and has no magnetic properties andtherefore not detectable. The stainless steel used in hypodermic needlesis typically austenitic 304 stainless steel, and therefore notdetectable.

Austenitic stainless steels are iron-chromium-nickel alloys withspecified but variable carbon content, which are not hardenable by heattreatment, and are regarded as non-magnetic due to the nickel present.Martensitic stainless steels are iron-chromium alloys with no or littlenickel content (less than 1%), hardenable by heat treatment, andregarded as magnetic. Ferritic stainless steels are iron-chromium alloyswith no or little nickel content (less than 1%), are not hardenable byheat treatment, and regarded as magnetic. Ferritic stainless steels havea lower carbon content than martensitic stainless steels. These termsare well known to those skilled in the art. 304 stainless steel is themost common grade of austenitic stainless steel. 420 stainless steel, amartensitic stainless steel, has a higher carbon content than 410stainless steel, the most common grade of martensitic stainless steel.430 stainless steel is the most common grade of ferritic stainlesssteel.

Since stainless steel disposable needles are desirable, applicantdecided to test other stainless steels to see if they could be detected.Applicant had no prior knowledge of whether magnetic stainless steeldisposable needles would be detected by metal detectors in meat packingplants. A martensitic 420 stainless steel welding rod was reduced toapproximately the size of a 20 gauge ½ inch needle for test purposes. Itwas then placed in meat and run through Loma and Safeline brand namemetal detectors on meat production lines and easily detected,unexpectedly and to the surprise of applicant and to the amazement ofeveryone else. No one at the meat plants believed that the experimentalrods of stainless steel that size could be detected. The experiment wasrepeated in 2 and 4 kilogram pork butts with bone, as bone is believedto affect metal detection, to convince both applicant and observer(packer). The 20 gauge ½ inch rod was detected on every trial. It wasdecided to manufacture a batch of needles for further testing.Unfortunately not only did 420 stainless prove impossible to obtain inthe tubular form necessary for needle manufacture, but so did othermartensitic stainless steels.

Ferritic stainless steel which is similar in composition, but notstructure, was considered as a possible alternative. Ferritic 430stainless steel was available in suitable tubular form. A small sampleof 20 gauge 1 inch disposable cannulae (needles without hubs) were madeup from this material and were similarly tested and detected. Again,applicant could not be certain before testing that the needles would bedetectable, and nobody else had any inkling that they would bedetectable. First 1 inch needles were tested in 2 and 4 kilogram porkbutts with bone on meat production lines using Loma and Safeline brandname metal detectors and detected on every trial. Needles were then cutin half to simulate 20 gauge ½ inch needles, which were then tested in 2and 4 kilogram pork butts with bone. Again, the needles were easilydetected on every trial, to the amazement of observers.

Ferritic cannulae, 20 gauge 1 inch, were made up with chromium platedbrass hubs as needles for injection testing. Generally, 430 stainlesshas lower tensile strength than 304 stainless so the question whetherferritic needles were as effective as austenitic needles arose. Theferritic needles were fitted onto a hypodermic syringe and tested byjabbing into a pork cadaver. Since the skin of pork cadavers toughensafter death, the needles were tested about twenty-four hours afterdeath. Forty-one punctures were made in the cadaver, using a singleneedle. When the 20 gauge needle deformed, it was finger straightened.The needle deformed with use, breaking at the forty first puncture. Asfar as applicant is aware this performance is comparable to existing 304stainless needles. Since 430 stainless has less tensile strength than304 stainless, the needle may deform and break with less use, but thepractical difference is small.

There was no prior reason to believe that martensitic or ferriticstainless steel in the dimensions of disposable hypodermic needles wouldbe detectable by metal detectors in meat production lines. There wasthus no inkling or useful intention to combine martensitic or ferriticsteel and the form of disposable hypodermic needles, which would beeasily and routinely detected by metal detectors in meat processinglines. These detectors are set at high sensitivity to attempt(unsuccessfully) to detect the austenitic needles. Applicant was notfaced with ignorance but active disbelief in the meat packing industry.Hearsay was not enough, demonstration was and is required to convincepeople.

The production batch of ferritic 430 stainless steel needles was made bycold drawing through a die from 2 inch diameter ⅜ inch wall thicknesstubular stock. Some needles were fitted with brass hubs, some withplastic hubs. The hubs can be brass, aluminum, plastic (oftenpolypropylene). Generally, several iterations of cold drawing arerequired. In the particular method used six were necessary.

By selecting magnetic stainless steel for disposable hypodermic needlesapplicant has solved a long standing problem in the meat industry.

As those skilled in the art would realize these preferred describeddetails and materials and components can be subjected to substantialvariation, modification, change, alteration, and substitution withoutaffecting or modifying the function of the described embodiments.

Although embodiments of the invention have been described above, it isnot limited thereto, and it will be apparent to persons skilled in theart that numerous modifications and variations form part of the presentinvention insofar as they do not depart from the spirit, nature andscope of the claimed and described invention.

1. A system for detecting whether a hypodermic cannulae cannula orportions a portion thereof embedded is present within a meat, samplefrom an animal, said system comprising;: a metal detector for detectingthe presence of whether metal embedded is present in a the meat sample;and a hypodermic cannula having a fluid passageway for injecting ordrawing fluid and being comprised at least in part of a stainless steelselected from magnetic a magnetically responsive martensitic stainlesssteel, ferritic stainless steel, mixtures of ferritic stainless steelmetals consisting of martensitic, ferritic, or and mixtures thereof,said metals of martensitic stainless steel, and said cannula having beenprepared by a plurality of cold drawings drawing and in having a sizegauge of between from 14 and to 20 gauge, wherein said cannula is moredetectable by said metal detector when said cannula or a portion thereofis present in the meat sample than a cannula or a portion thereof ofcomparable size and made of standard austenitic stainless steel.
 2. Thesystem as set forth in claim 1, wherein said martensitic stainlesssteel, consists of comprises 420 stainless steel.
 3. The system as setforth in claim 1, wherein said ferritic stainless steel, consists ofcomprises 430 stainless steel.
 4. A hypodermic needle cannula or portionthereof having high detectability in a meat sample, comprising: a metalselected from magnetic stainless steel metals consisting of martensitic,ferritic, or mixtures thereof, said metals prepared, in a preparationstep by a plurality of cold drawings and in a size gauge of between 14and 20, whereby detectability of said needle cannula or portion thereofprepared according to said preparation step is greater than thoseprepared in the absence of said preparation step.
 5. The hypodermicneedle cannula as set forth in claim 4, wherein said stainless steel isselected from the group consisting of 430 and 420 stainless steel, ormixtures thereof.
 6. A method of detecting hypodermic needle cannulae orportions thereof embedded within a meat sample, comprising: providing ahypodermic needle cannula or portion thereof to as set forth in claim 4;providing a metal detector for detecting the presence of metal in a meatsample; providing a meat sample for exposure to said metal detector;exposing said sample to said detector; and detecting the presence ofsaid needle cannula or portion thereof.
 7. The system as set forth inclaim 1, wherein said stainless steel of said cannula comprises at leastin part ferritic stainless steel and martensitic stainless steel.
 8. Themethod as set forth in claim 15, wherein said stainless steel comprisesat least in part a mixture of 430 stainless steel and 420 stainlesssteel.
 9. A method for injecting an animal with a hypodermic cannula,said method comprising: providing a hypodermic needle cannula preparedby cold drawing and having a size ranging from 14 to 20 gauge, theneedle cannula having a fluid passageway for injecting fluid into ordrawing fluid from the animal and comprising at least in part amagnetically responsive stainless steel selected from martensiticstainless steel, ferritic stainless steel, mixtures of ferriticstainless steel, and mixtures of martensitic stainless steel wherein thecannula is more detectable by a metal detector when the cannula or aportion thereof is present in the meat sample than a cannula or aportion thereof of comparable size and made of standard austeniticstainless steel; injecting the animal with the hypodermic needlecannula; and subsequently detecting with a metal detector whether thehypodermic cannula or a portion thereof is present in a meat sample fromthe animal.
 10. The method of claim 9, wherein said metal comprisesmartensitic stainless steel and ferritic stainless steel.
 11. The methodof claim 9, wherein said metal comprises ferritic stainless steel.
 12. Amethod of detecting whether a hypodermic needle cannula or a portionthereof is present within a meat sample of an animal, said methodcomprising: providing a meat sample from an animal that has beeninjected with a hypodermic needle cannula, the needle cannula having afluid passageway for injecting fluid into the animal or drawing fluidfrom the animal and comprising at least in part a magneticallyresponsive stainless steel selected from martensitic stainless steel,ferritic stainless steel, mixtures of ferritic stainless steel, andmixtures of martensitic stainless steel, the cannula being prepared bycold drawing and having a size from 14 to 20 gauge, and wherein thecannula or a portion thereof is more detectable by a metal detector whenthe cannula or a portion thereof is present in the meat sample than acannula or a portion thereof of comparable size and made of standardaustenitic stainless steel; providing a metal detector for detecting thepresence of metal in the meat sample; exposing the meat sample to themetal detector; and detecting with the metal detector whether the needlecannula or a portion thereof is present in the meat sample with themetal detector.
 13. The method as set forth in claim 15, wherein saidmartensitic stainless steel comprises 420 stainless steel.
 14. Themethod of claim 12, wherein said metal comprises martensitic stainlesssteel and ferritic stainless steel.
 15. The method of claim 12, whereinsaid metal comprises ferritic stainless steel.